Effects of GBR and Delayed Loading on Bone Ring Grafting with Simultaneous Implant Insertion: an Experimental Study on Beagle Dogs

Objective To determine the effects of guided bone regeneration (GBR) and delayed loading on autogenous bone ring grafting. Methods Autogenous bone ring augmentation with simultaneous implant insertion was performed in the mandibular premolars region of six Beagle dogs. The Bone quality of four mandibular premolars 〔second premolar （P2） and fourth premolar （P4)〕 were detected using cone beam CT (CBCT). The P2s and P4s of bilateral mandible were extracted, with three extracting sites being randomly selected to create buccal defects and the remaining one serving as control. GBR and bone ring grafting with simultaneous implant insertion was performed on two of the three experimental sites with buccal defects 3 months later, while the other one was treated with bone ring grafting with simultaneous implant insertion. Routine implant placement was performed in the control group. Vertical bone resorption and sulcus deep around the implants were measured three months after occlusal loading with abutment. Results Three months after operations, 83.3% of bone rings grafts were successful and 100% of implants survived. Delayed healing appeared more in the dogs with GBR compared those treated with bone ring grafting with simultaneous implant insertion, resulting in an increase in vertical bone resorption. Compared with the control group, delayed loading had no effects on vertical bone resorption and the health of gingiva tissues after autogenous bone ring transplant. Conclusion GBR is not a preferred procedure for bone ring grafts, which may increase the risk of delayed healing and site infections, leading to failure of implants. Healed bone ring grafts can resist loadings as normal.